The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Tag: Improvements

Making the world a better place, one piece at a time

Layered Paper: Cutting & Assembly Fixtures

Time spent making a fixture is never wasted time:

Layered Paper cutting fixture – in use

The general idea: securely hold a piece of paper flat while cutting it, so that it cannot move or warp, while letting the cut pieces fall out without snagging on anything underneath. The sheet holder I made a while ago worked reasonably well, but those thin metal blades tend to warp while cutting small patterns in restricted areas and the pieces definitely don’t fall free.

The simple fixture I use while assembling the paper layers consists of four rivnuts poking through a chipboard upper layer, with a craft paper layer around the rivnut washers on the bottom:

Layered Paper – alignment fixture

The cutting fixture uses a similar layout around a hole for freely falling chips:

Layered Paper cutting fixture – installed

Next time, I’ll remove those three bars across the hole, because the MDF doesn’t need any support. Nearly all the chips fell out, so the fixture worked as intended.

I trimmed the flange off the rivnuts so they would sit flat on the MDF:

Layered Paper cutting fixture – trimming rivnut flange

That’s the kind of job chuck stops really simplify.

The cutting fixture requires pre-cutting paper into 200 mm squares with four 5 mm corner holes, which can be done three-abreast on the platform bars, then putting each sheet in the fixture to cut the shapes. That’s not much of a disadvantage compared to messing up an unsupported sheet.

The cutting fixture has crosshair targets to align a LightBurn template using Print-and-Cut, thus eliminating the need to precisely locate the fixture on the platform. The finger-crushingly strong neodymium bar magnets do a fine job of holding the MDF in place on the steel platform.

The small cutout rectangle in the lower right corner frames the sheet number, done in binary code with 0 = 1 mm circle and 1 = 2 mm circle:

Layered Paper cutting fixture – layer binary code

That’s the underside view of a completed stack with the 5 mm lower-right fixture hole on the left and the code for layer 11 = 0b1011 reading backwards. The small 0 holes have two lobes showing the Print-and-Cut alignment was off by maybe 0.3 mm; the off-center hole was in the blank sheet.

Obviously, cutting tiny circles with a big laser at 300 mm/s doesn’t produce perfect results. You can see small wiggles in larger shapes:

Layered Paper cutting fixture – cut wobbles

Unless you’re trying hard to find a problem, you’ll never notice them.

2023-10-19
Layered Paper: Chimney Swallows Block

The Chimney Swallows block from page 128 of Beyer’s book:

Chimney Swallows – Beyer 128

The tool (blue & orange) and top cut (red) layers:

Chimney Swallows – LB layout

The long radial blue tool lines simplified selecting them when mirroring / duplicating the cut polygons around their symmetries. The orange tool circles aligned various midpoints / vertices / features during construction.

The inward curve along the outer edge started as a triangle with a node at about the middle of the curve. Deleting that node left the remaining two sides overlapped, but dragging one of them to match the curve worked OK. There’s probably a better way.

That curve defines the outer edges of the shapes along it, so I drew polygons from the corner intersections and dragged the outer edge to match the curve at high zoom.

The shape remains selected after dragging the side, which meant I could immediately apply a 1 mm inset to create the cut lines.

To my surprise, the swallow bodies are straight-sided polygons!

After taking advantage of all the symmetries, knock out the shapes defining each layer:

Chimney Swallows – LB paper cuts

The swallows look like F-117 Nighthawks to me:

Layered Paper – Chimney Swallows – Beyer 128

Maybe I have the colors wrong:

Layered Paper – Chimney Swallows – Beyer 128

Fly away!

2023-10-18
Layered Paper: Pyrotechnics Block

Starting from the Pyrotechnics quilt block on page 132 of Beyer’s book:

Pyrotechnics – Beyer 132

It looks more like flowers than fireworks to me, but there’s no accounting for taste.

Deploy enough 2 mm circles to catch the flower’s radial symmetry:

Pyrotechnics – LB layout

During the process of building the layout, a big circle positioned the cups at the base of the flowers, another delineated the joint between the cups and the petals, and more little circles caught the intersection of those circles with the petals. All that was for visualization and positioning, as you only draw one flower shape, then duplicate it around the pattern.

Although the cups and petals are surely circular arcs, it’s easier to draw a closed line triangle around the intersections, then pull the midpoint of a line into an arc (Bezier curve!) matching the pattern Closely Enough™ at high zoom. Because the arcs end at the intersection points based on circular arrays of points, they’ll all match up when they’re duplicated around the pattern; in fact, you need only one side of one petal, mirror it around the midline, and away you go.

Then the magic happens:

Pyrotechnics – LB tool insets

Which is easier to see without the original shapes:

Pyrotechnics – LB insets

Pick one of the closed shapes, apply the Offset tool to shrink it by 1 mm, duplicate as needed, and you get the outlines of the regions to cut with 2 mm between them. Plunk those shapes on a cutting layer, add the outer frame with locating holes for the fixture, and it’s ready to cut the top layer from black paper:

Pyrotechnics – LB cuts

Knock out the cuts for each sheet of paper in the stack:

Pyrotechnics – LB paper cuts

Then Fire The Laser™:

Layered Paper – Pyrotechnics – Beyer 132

That was a nearly random selection of colors, but it’s hard to go wrong.

IMO, a frame makes it look even better:

Layered Paper – Pyrotechnics – Beyer 132

This could be Art.

2023-10-17
Moonlander Keyboard vs. Board Chow

The Moonlander keyboard has per-key LEDs that I’ve denatured enough that most show a pale gray, with a few others highlighted in orange. A few weeks ago the LEDs on the right-hand thumb cluster and the N key went nuts, cycling through a surprising assortment before settling on bright red; the obvious resets / firmware reflashing / tapping were all unavailing.

ZSA’s tech support recommended taking the thumb cluster apart to check the ribbon cable connecting it to the main keyboard half:

Moonlander thumb cluster – PCB bottom

Come to find out my unclean personal habits lodged a particularly corrosive nugget of board chow on the cable:

Moonlander – corroded ribbon cable

It’s a more-or-less standard 0.5 mm pitch cable, but only 20-ish mm long, much shorter than the cables carried by the usual sources. ZSA sells them for $2 each, plus $25 courier shipping, so I bought three; they arrived in two days from halfway around the planet.

Because I don’t foresee my personal habits changing any time soon, I tucked a Kapton tape snippet in the gap to serve as a gutter:

Moonlander thumb cluster – tape shield installation

That’s with the two hinge screws out and the cluster eased down-and-away from the keyboard enough to get the tape pressed against the keyboard.

With the screws installed and the cluster at its normal most-downward angle, the gutter closes up:

Moonlander thumb cluster – tape shield folded

With the cluster in its normal operating position (for me, anyway), the gutter is nearly invisible:

Moonlander thumb cluster – normal position

For the record, I tucked the remaining ribbon cables inside the left-hand thumb cluster against future need.

2023-10-09
Laser Cutter: Moving Mirror 3

With Mirror 1 and Mirror 2 aligned, the next step is positioning the laser head to put the beamline at the center of both the aperture and Mirror 3 inside:

OMTech CO2 Mirror 3 mount – realigned – Z screws

Raising the laser tube by 5 mm put the head’s Z axis screws in the middle of their slots. This had the additional benefit of letting me rotate the head slightly around the X axis to make it perpendicular with the bed, thus fixing its mysterious from-the-factory misalignment.

Centering the beamline horizontally required a few iterations of Mirror 2’s position along the Y axis, but eventually produced this result:

Beam Alignment – Mirror 3 detail – 2023-09-16

Those are five manual pulses with the head at the corners and center of the platform. I put the 3M target on the mirror rotated 90° from the proper orientation with the stretched scale aligned vertically and parallel to the slightly oval beam mark.

The F target shows the beam position inside the head just above the focus lens:

Beam Alignment – Focus detail – 2023-09-16

The little target in the middle gets centered on the nozzle by feel and shows the beam position within a 2 mm circle. The initial position was off against the side of the nozzle, but slight twiddling of the Mirror 3 screws centered it.

I centered the lower F target at the beam position using the red dot aiming pointer, then pulsed the laser to put a pinhole almost exactly at the graticule center. The larger scorch shows the beam size with the platform lowered 10 mm from the focus level. The Z axis leadscrews are not particularly precise and the platform moves by about a millimeter in X and Y as they rotate, so that’s about as good as it gets.

After all that, the laser behaves at least as well as it ever did and I feel better about having the beamline actually travel along the center of the optical path.

Now, back to cutting out interesting shapes …

2023-10-06
Laser Cutter: Moving Mirror 2

With Mirror 1 moved 10 mm to the right (as seen from the front of the cabinet), Mirror 2 must move 5 mm to fix the problem that started this whole thing and put the beam in the center of the mirror:

Beam Alignment – 2M detail – 2023-09-16

This puts the bracket holding Mirror 2 closer to the center of its x axis adjustment range:

OMTech CO2 Mirror 2 mount – realigned – X screws

Remember, the flange is fixed to the gantry and the bolts move with the mirror mounting bracket.

Raising the laser tube by 5 mm requires Mirror 2 to go upward by a bit to put the beam at the center:

OMTech CO2 Mirror 2 mount – realigned – YZ screws

The least awful way to make simultaneous X and Z axis adjustments seems to be by feel. Tighten the screws just enough to prevent the bracket from moving easily, then slide it while aligning the top edge with respect to the flange on the gantry.

When it feels about right, stick a target to the aperture, fire a pulse, check the results, and iterate until it is actually right.

The two screws holding the mirror mount to the bracket sit in slots allowing some adjustment in the Y axis, as well as a slight amount of rotation. AFAICT, the mount was rotated enough that the test pulses passed through the center of the aperture, but hit the mirror off-center as shown in the top picture. I aligned the aperture parallel with gantry, which should put the holder at 45° to the beamline, and hoped for the best.

With the pulse mostly centered, twiddle Mirror 1’s alignment to make the beam parallel to the Y axis, which eventually produced these results, with each target getting a pulse at each end of the Y axis travel:

Beam Alignment – Mirror 2 detail – 2023-09-16

Not perfect, but much better than where it started.

2023-10-05
Laser Cutter: Moving Mirror 1

Raising the laser tube 5 mm required nothing more than cutting and inserting 5 mm spacers and finding slightly longer M4 screws:

OMTech CO2 laser tube – 5 mm Z supports

I used an ancient adjustable inside caliper to put the tube the same distance from and aligned parallel to the partition.

Sliding the tube an inch to the left provided enough space to drill & tap two new holes for the Mirror 1 mount to move the beamline 10 mm along the X axis:

OMTech CO2 Mirror 1 mount – redrilled screw holes

I briefly considered crunching rivnuts in there, but the mirror mount expects to sit flat on the floor with no room for rivnuts. So it goes.

Although Mirror 1’s mount has some vertical adjustment, the central stem was already close to its maximum extension, so I cut a 5 mm plywood pad to raise the base:

Laser Mirror 1 – baseplate scan

Despite what the lighting suggests, it’s concave. The image was clean and contrasty enough to just trace into vectors with LightBurn, then Fire The Laser to cut the spacer:

OMTech CO2 Mirror 1 mount – 5 mm Z shim

If you’re wondering how that worked with the tube jacked up, Mirror 1 sitting on the scanner, and the beamline in disarray, there’s considerable benefit in doing things out of the obvious narrative sequence.

Reassemble the mirror, square the entrance aperture to the partition, fire a couple of test shots to center the mirror on the beamline:

Beam Alignment – Mirror 1 detail – 2023-09-16

And that part’s done.

2023-10-04